Esters of capsaicin for treating pain

ABSTRACT

The present invention relates to the formulations of ester derivatives of capsaicin and ester derivatives of myristoleic acid. These derivatives are capable of reverting to the active parent compound following enzymatic or chemical hydrolysis. These derivatives have a higher lipophilicity, lipid solubility and less irritation to the skin than the parent compound, and hence are better able to be incorporated into certain pharmaceutical formulations, including cream and ointment pharmaceutical formulations. The pharmaceutical compositions of the present invention contain a compound of following formula (Ia):
 
R—CO-CAP  (Ia)
 
wherein CAP refers to collectively the capsaicins represented in FIG.  1  and a compound of formula (Ib):
 
MCO-O—R  (Ib)
 
wherein MCO refers to myristoleic acid.
 
     In formulae Ia and Ib, R is selected from alkyl groups of up to about 18 carbon atoms and aryl groups of up to about 18 carbon atoms and alkylene group of up to about 18 carbon atoms and an arylene group of up to about 18 carbon atoms. The alkyl, aryl and alkylene groups may be substituted or un-substituted, branched or straight chains. In addition, R may contain heteroatoms and may be straight chained or branched. 
     The pharmaceutical compositions containing compounds of formulae Ia and Ib are useful for pain management in mammals in vivo and have been contemplated to be used in the treatment of various pains in humans.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Patent ApplicationSer. No. 60/832,599, filed Jul. 24, 2006 by the present inventors.

FEDERALLY SPONSORED RESEARCH

None

SEQUENCE LISTING OR PROGRAM

None

FIELD OF INVENTION

This invention relates to a treatment for pain. More specifically itrelates to the use of esters of capsaicin for the treatment of pain.Even more specifically it relates to the use of esters of capsaicin andester derivatives of myristoleic acid for the treatment of pain.

BACKGROUND OF THE INVENTION

Capsicum consists of the dried ripe fruits of Capsicum annuum Roxb.(Family Solanaceae), a small erect shrub indigenous to tropical America,cultivated in South America, China, India and Africa. Capsicum containsa crystalline pungent principle capsaicin, traces of a liquid alkaloid,red coloring matter and a fatty oil. In folk medicine, capsicum isregarded as an aphrodisiac, depurative, digestive, stomachic,carminative, antispasmodic, diaphoretic, antiseptic, counterirritant,rubefacient, styptic, and tonic. Internally, capsicum has been used totreat asthma, pneumonia, diarrhea, cramps, colic, toothache, flatulentdyspepsia without inflammation; insufficiency of peripheral circulation;as a gargle for sore throat, chronic pharyngitis and laryngitis; andexternally as a lotion or ointment to treat neuralgia, includingrheumatic and arthritic pain, and unbroken chilblains (cold injuries)(Duke, 1985; Leung and Foster, 1996; Newall et al., 1996).

In Germany, cayenne pepper is official in the German Pharmacopeia andapproved in the Commission E monographs as a topical ointment for therelief of painful muscle spasms in the upper torso (DAB, 1997). In theUnited States, capsicum tincture and oleoresin were formerly official inthe United States Pharmacopeia and National Formulary. Capsicum USP wasused as a carminative, stimulant, and rubefacient (Leung and Foster,1996; Taber, 1962).

The most potent and predominant chemical entity in capsicum is capsaicin(0.14%) (Cordell and Araujo, 1993; FIG. 1). The heat sensation of purecapsaicin is approximately 16 million Scoville heat units (SHU) and isso hot that in its pure form diluted one hundred thousand fold it cancause blistering of the tongue. A series of homologous branched- andstraight-chain alkyl vanillylamides, collectively known ascapsaicinoids, is present in lesser concentrations than the parentcompound, capsaicin. Of the capsaicinoid fraction, capsaicin (48.6%) isquantitatively followed by 6,7-dihydrocapsaicin (36%),nordihydrocapsaicin (7.4%), homodihydrocapsaicin (2%), and homocapsaicin(2%) (Duke, 1985). Capsaicinoids and capsaicin are collectively found inamounts of 0.1% to 1%, with quantities varying according to soil andclimate (Rumsfield and West, 1991).

Capsaicin, a colorless crystalline substance, was first synthesized in1930. Capsaicin has been studied since the mid-19th century and itsstructure is elucidated as 8-methyl-6-nonenoyl vanillylamide (Cordelland Araujo, 1993). Most pharmacological studies performed with isolatedconstituents of chile pepper have focused on capsaicin, which is themajor pungent constituent.

The crude extract of capsicum fruits, known as capsicum oleoresin,contains at least 100 different volatile chemical constituents, andtherefore may function in differing ways from pure capsaicin. Thus, itis important to distinguish between studies using capsaicin and thoseemploying capsicum oleoresin (Cordell and Araujo, 1993).

Nonivamide (pelargonic acid vanillylamide) is a common syntheticadulterant of capsicum products. Although structurally different fromcapsaicin, its presence in capsicum or capsaicin samples can be detectedspectrographically and there is no evidence that this compound occursnaturally in Capsicum (Cordell and Araujo, 1993).

Capsaicin affects lipid metabolism as demonstrated in a study by Kawadaet al. (1986). Male rats fed a diet containing 30% lard with capsaicinat 0.14% of the diet developed serum triglyceride levels that weresignificantly lower than those of animals receiving a high-fat dietwithout capsaicin. But levels of free fatty acids, cholesterol, andpre-beta-lipoprotein were not affected. Activities of liver enzymesinvolved in lipid synthesis (acetyl-CoA carboxylase) and in carbohydratemetabolism (glucose-6-phosphate dehydrogenase) were inhibited in thehigh-fat diet, but the activity of the latter was restored to controllevels by the added dietary capsaicin. The weight of perirenal adiposetissue was reduced in a dose-dependent manner by capsaicin. Theseresults suggested that capsaicin did not interfere with lipidbiosynthesis. Rather, that capsaicin might stimulate lipid metabolism,and possibly facilitates mobilization of lipid from adipose tissue.

In a follow-up to the study above, Kawada et al. (1986a) measured theeffect of i.p. administered capsaicin on general energy metabolism,including oxygen consumption, respiratory quotient, and substrateutilization. Capsaicin had a general stimulatory effect on metabolism,similar to that of epinephrine; oxygen consumption was elevated,respiratory quotient was initially elevated, then decreased; and serumglucose and insulin levels were elevated, concomitant with a rapiddecrease in liver glycogen, and a gradual increase in serumtriglycerides. The response was blocked by beta-adrenergic blockers, butwas not effected by alpha-adrenergic or ganglion blockers. Their resultssuggested that capsaicin effects metabolism either as a directbeta-adrenergic agonist, or indirectly by stimulating catecholaminerelease.

Yamato et al. (1996) showed that capsaicin produced a markedconcentration-dependent decrease in the amplitude, the rate of rise, andthe rate of relaxation of the contractile tension of rat ventricularpapillary muscles; however, the half-life of the relaxation and the timeto peak tension were only slightly effected. Calcium release andshortening of action potential duration in ventricular myocytes wasprofoundly reduced by capsaicin, perhaps resulting from the non-specificmembrane-stabilizing effects of capsaicin.

Capsaicin treatment caused a biphasic effect on contractile force, leftventricular systolic blood pressure, and heart rate of isolated perfusedrat hearts. A transient initial increase in contractile force and leftventricular systolic pressure was observed, followed by a prolongeddepression of both parameters. Heart rate was increased, but this effectwas not followed by a subsequent reduction. The initial increases incontractile force and blood pressure could have been induced by therelease of calcitonin-gene-related peptide (CGRP) from local sensorynerves; the negative inotropic effects following the initial increasemay be due to a direct inhibitory effect of capsaicin on ventricularcells, or to nonspecific membrane-stabilizing effects. The increasedheart rate was attributed to the release of CGRP (Lundberg 1985).

Capsaicin elicits a vasoconstrictive response in the large cerebralarteries of the cat (Saito et al., 1988), and in the middle and basilarcerebral arteries, an effect was attributed to a direct contraction ofsmooth muscle, since the response was independent of the presence ofendothelium and nerve components. However, Saito et al. found resultssuggesting that while capsaicin releases and depletes vasodilatorpeptides from perivascular nerves, the direct vasoconstrictor effects ofcapsaicin overwhelm the vasodilator effects of these peptides.

An increased activity of CGRP-containing trigeminovascular nerve fibreshas been correlated to the pathophysiology of migraine (Buzzi et al.,1991) either during attacks (Goadsby et al., 1990; Goadsby & Edvinsson,1993) or as ageneral imbalance in migraine patients (Ashina et al.,2000). Therefore, clinical potentials of CGRP receptor-antagonists inthe treatment of migraine have been addressed (Doods et al., 2000).Capsaicin (Holzer, 1991b; Szallasi & Blumberg, 1999) potently andselectively causes release of CGRP from sensory nerve terminals both invitro and in vivo (Duckles & Levitt, 1984; Duckles, 1986; Holzer, 1991a;Saito & Goto, 1986; Wharton et al., 1986). The mechanism ofcapsaicin-induced CGRP depletion involves binding of capsaicin tovanilloid 1 receptors (VR1) (Caterina et al., 1997).Capsaicin-association to VRs triggers Ca2+ influx and elevatedintracellular calcium levels in turn stimulate CGRP-release. Thevanilloid 1 receptor is in addition to capsaicin stimulated by heat,hydrogen ions, lactate (Franco-Cereceda & Liska, 2000; Franco-Cereceda,1988) and the endogeneous cannabinoid, anandamide (Zygmunt et al.,1999).

A hypoxic reflectory release of CGRP which has been suggested inmyocardium (Kallner, 1998; Dai et al., 2000; Franco-Cereceda & Liska,2000) and in cerebral arteries (McCulloch et al., 1986) may be due tostimulation of this receptor as well. It has previously beendemonstrated that CGRP, rather than SP and NKA, is responsible for thecapsaicin-induced vasodilatation of guinea-pig basilar artery(Franco-Cereceda & Rudehill, 1989; O'Shaughnessy et al., 1993;Jansen-Olesen et al., 1996).

In tests using cultured human intestinal epithelial cells,Jensen-Jarolim et al. (1998) found sufficient in vitro evidence tosuggest that Capsicum may increase the permeability of thegastrointestinal tract to allow transport of macromolecules and ionsacross the epithelium; an effect, they add, that might have importanceto food intolerance and allergic reactions to food. The stimulatoryeffect of orally administered capsaicin on gastric acid secretion andmucosal blood flow was studied in rats using amounts roughly equivalentto a normal Thai diet. Capsaicin was noted to have a protective effecton gastric mucosa of ethanol-induced gastric lesions in rats (Uchida etal., 1991). The protective effect was attenuated upon pretreatment withindomethacin and disappeared in capsaicin-sensitive nerve-degeneratedrats, suggesting that enhanced prostaglandin formation inhibited lesionformation. Further study by the same group found decreased stomachmotility and increased mucosal blood flow with intragastric capsaicintreatment, whereas capsaicin pre-treatment desensitized the afferentneurons, thereby mitigating this protective effect.

An in vitro chemopreventive activity of capsaicin was shown by Morr etal. (1995). When capsaicin was added to cultured cells of Caov-3 humanovarian carcinoma, MCF-10A human mammary adenocarcinoma, HL-60 humanpromyelocytic leukemia, and HeLa cells, a preferential growth-inhibitionwas evident as cells became smaller and underwent cell death. Condensedand appearing fragmented, the nuclear DNA of these cells suggested thatcapsaicin had induced apoptosis.

The arachidonic acid cascade is an important component of inflammationand the associated localized immune response. The release of arachidonicacid (AA) from membrane phospholipids and subsequent leukotrienebiosynthesis occurs during inflammation, and products formed by AAoxidation act in concert with numerous other factors, includingcytokines, PAF (platelet-activating factor), nitrogen oxide, andhistamine, all of which are important mediators of the immune response.A study (Panossian et al., 1996) found that at low concentrationscapsaicin stimulated the production of interleukin-1a, while at higherdoses it inhibited this response. Capsaicin caused a dose-dependentrelease of AA from PMNs (poly-morphonuclear leukocytes), and a similarconcentration-dependent conversion of the AA metabolites, prostaglandinE2 (PGE2) and LTB4. When incubated with granulocytes, capsaicin causedan increased synthesis of 12-HETE, an eicosanoid metabolite of AA, butat the same time was found to cause a dose-dependent decrease of allproducts of 5-lipoxygenase. These results suggested that thedose-dependent reversible effects of capsaicin on immune cells andinterleukin-1alpha are closely associated with arachidonic acidmetabolism (Panossian et al., 1996).

Viral replication, immune regulation, and induction of variousinflammatory and growth-regulatory genes require activation of a nucleartranscription factor (NF)-κ-B. Agents that can block NF-κ-B activationhave potential to block downstream responses mediated through thistranscription factor. Capsaicin (8-methyl-N-vanillyl-6-nonenamide) hasbeen shown to regulate a wide variety of activities that require NF-κ-Bactivation (Singh 1996). The pretreatment of human myeloid ML-1a cellswith capsaicin blocked TNF-mediated activation of NF-κ-B in a dose- andtime-dependent manner. Capsaicin treatment of cells also blocked thedegradation of I-κ-B alpha, and thus the nuclear translocation of thep65 subunit of NF-κ-B, which is essential for NF-κ-B activation.TNF-dependent promoter activity of I-κ-B alpha, which contains NF-κ-Bbinding sites, was also inhibited by capsaicin.

Neurogenic inflammation has been successfully modeled using capsaicin.When injected intradermally, capsaicin evokes a temporary burningsensation lasting 3 to 5 minutes and a characteristic localized flareconsisting of a red flush with slight edema (Holzer 1988). The capsaicinflare is thought to be induced by a local axon reflex involving releaseof neuropeptides such as SP and CGRP from sensory neurons (Holzer 1988).Additional mediators of the capsaicin flare are thought to includecytokines, prostaglandins, and other neuropeptides (Holzer 1991;Veronesi 1999). Within normal individuals, the size of the capsaicinflare over time is quite consistent (Jolliffe 1995).

The effect of glucocorticoids and catecholamines on thecapsaicin-induced flare have been minimally examined. However,glucocorticoids have not been shown to block the capsaicin-induced flare(Ahluwalia 1994). Alpha adrenoreceptors are known to be involved in thepain response to capsaicin (Kinnman 1997).

Depending on the concentration used and the mode of application,capsaicin can selectively activate, desensitize, or exert a neurotoxiceffect on small diameter sensory afferent nerves while leaving largerdiameter afferents unaffected (Holzer, 1991; Winter et al., 1995).Sensory neuron activation occurs due to interaction with a ligand-gatednonselective cation channel termed the vanilloid receptor (VR-1)(Caterina et al., 1997), and receptor occupancy triggers Na⁺ and Ca²⁺ion influx, action potential firing, and the consequent burningsensation associated with spicy food or capsaicin-induced pain. VR1receptors are present on both C and Aδ fibers, and can be activated bycapsaicin and its analogs, heat, acidification, and lipid metabolites(Tominaga et al., 1998; Caterina and Julius, 2001). Desensitizationoccurs with repeated administration of capsaicin, is a receptor-mediatedprocess, and involves Ca²⁺- and calmodulin-dependent processes andphosphorylation of the cation channel (Winter et al., 1995; Wood andDocherty, 1997).

Capsaicin induces release of substance P and calcitonin gene-relatedpeptide from both peripheral and central terminals of sensory neurons,and desensitization inhibits such release (Holzer, 1991); suchinhibition may result from inhibition of voltage-gated Ca²⁺-currents(Docherty et al., 1991; Winter et al., 1995). Neurotoxicity is partiallyosmotic and partially due to Ca²⁺ entry with activation ofCa²⁺-sensitive proteases (Wood et al., 1989; Winter et al., 1995). Inneonates, neurotoxicity can be lifelong (Janscó et al., 1977), whereasin adult animals receiving a localized dose, a reversible injury mayoccur as cell bodies capable of regeneration are left intact (Holzer,1991). Both desensitization and neurotoxicity lead to analgesia inrodent paradigms, with specific characteristics of analgesia dependingon the dose of capsaicin, route of administration, treatment paradigm(i.e., acute or repeated administration), and age of the animal (Holzer,1991; Winter et al., 1995). The topical skin application of capsaicin torodents produces analgesia (Kenins, 1982; Lynn et al., 1992), butvariability in outcome can occur due to the concentration, the number ofapplications, and the different vehicles used that can affect the rateand extent of skin penetration (Carter and Francis, 1991; McMahon etal., 1991).

The distribution and metabolism of capsaicin and/or dihydrocapsaicin hasbeen studied in rats. Capsaicin is distributed to the brain, spinalcord, liver and blood within 20 mins. of i.v. administration. Oral dosesof dihydrocapsaicin in the rat showed metabolic activity associated withits absorption into the portal vein. Capsaicin and dihydrocapsaicin aremetabolized in the liver by the mixed-function oxidation system(cytochrome P-450-dependent system). It is assumed that capsaicin isexcreted in urine. In rats, most of dihydrocapsaicin is known to berapidly metabolized and excreted in the urine (Rumsfield and West,1991).

Acute intradermal injection of capsaicin to the skin in humans producesa burning sensation and flare response; the area of application becomesinsensitive to mechanical and thermal stimulation, the area of flareexhibits a primary hyperalgesia to mechanical and thermal stimuli, andan area beyond the flare exhibits secondary allodynia (Simone et al.,1989; LaMotte et al., 1991). Repeated application to normal skinproduces desensitization to this response and thus forms the basis ofthe therapeutic use of topical capsaicin in humans. Desensitizationinvolves both physiological changes in the terminals of the sensoryneuron noted above, as well as a degree of loss of sensory fiberterminals within the epidermis (Simone et al., 1989; Nolano et al.,1999). With respect to topical applications of capsaicin, it has beenestimated that assuming 100% of a topically-applied dose is absorbedinto the body, an application of 90 g capsaicin (2 tubes of cream,0.025% capsaicin) per week would result in a daily exposure of 0.064mg/kg capsaicin for a 50 kg person. This represents less than 10% of thedietary intake of a typical Indian or Thai diet (Rumsfield and West,1991).

Topical capsaicin preparations of 0.025 and 0.075% are available forhuman use, and these produce analgesia in randomized double-blindplacebo-controlled studies, open label trials, and clinical reports(Watson, 1994; Rains and Bryson, 1995). Capsaicin, is recognized by theU.S. FDA as a counterirritant for use in OTC topical analgesic drugproducts (Palevitch and Craker, 1995). It is used as a component invarious counterirritant preparations (Leung and Foster, 1996), includingArthriCare® (Del Pharmaceuticals, Inc.) arthritis pain relieving rub,which contains Capsicum oleoresin (0.025% capsaicin) in combination withmenthol USP and Aloe vera gel (Arky et al., 1999). Capsicum ointments,such as Zostrix® cream (GenDerm Corp.), containing 0.025% or 0.075%capsaicin, are used topically to treat shingles (herpes zoster) andpost-herpetic neuralgia (Bernstein et al., 1987; Der Marderosian, 1999;Palevitch and Craker, 1995).

Topical capsaicin produces benefit in post-herpetic neuralgia (Bernsteinet al., 1989; Watson et al., 1993), diabetic neuropathy (Capsaicin StudyGroup, 1992), postmastectomy pain syndrome (Watson and Evans, 1992; Diniet al., 1993), oral neuropathic pain, trigeminal neuralgia, andtemperomandibular joint disorders (Epstein and Marcoe, 1994; Hersh etal., 1994), cluster headache (following intranasal application; Marks etal., 1993), osteoarthritis (McCarthy and McCarthy, 1992), anddermatological and cutaneous conditions (Hautkappe et al., 1998).Whereas pain relief is widely observed in these studies, the degree ofrelief is usually modest, although some patients have a very goodresult. Topical capsaicin is generally not considered a satisfactorysole therapy for chronic pain conditions and is often considered anadjuvant to other approaches (Watson, 1994). No significant benefit wasreported in chronic distal painful neuropathy (Low et al., 1995) or withhuman immunodeficiency virus-neuropathy (Paice et al., 2000).

Capsaicin produces marked alterations in the function of a definedsubpopulation of unmyelinated sensory afferents, termed C-polimodalnociceptors. Following the initial period of intense burning or stingingpain accompanied by erythema, topical capsaicin application causesinsensitivity to further irritation by a variety of noxious stimuli.Accordingly, topical preparations of capsaicin find use as a topicaltherapy for a variety of cutaneous disorders that involve pain anditching, such as post-herpetic neuralgia, diabetic neuropathy, pruritus,psoriasis, cluster headache, postmastectomy pain syndrome, rhinopathy,oral mucositis, cutaneous allergy, detrusor hyperreflexia, loinpain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy, pain due to skin tumor and arthritis (Hautkappeet al., 1998).

The most frequently encountered adverse effect with capsaicin is burningpain at the site of application, particularly in the first week ofapplication. This can make it impossible to blind trials and can lead todropout rates ranging from 33 to 67% (Watson et al., 1993; Paice et al.,2000). Another factor in compliance is the time delay before therapeuticeffect is observed (at least a week, but sometimes several weeks). Oneapproach toward minimizing adverse effects and accelerating the rate ofanalgesia has been to deliver a higher capsaicin concentration (5-10%)under regional anesthesia, and this produced sustained analgesia lasting1 to 8 weeks in cases of complex regional pain syndrome and neuropathicpain (Robbins et al., 1998). When topical local anesthetics were appliedwith 1% topical capsaicin, no alteration in pain produced by thecapsaicin was observed in healthy subjects (Fuchs et al., 1999)indicating that this co-treatment was not sufficient to block the paininduced by capsaicin.

Because of intense burning or stinging pain, many patients are nottolerated in the long-term treatment with topical capsaicin and,therefore, have to discontinue the treatment before appearance ofanalgesic effect of capsaicin through prolonged administration. It wasreported that 26 out of 39 (66.7%) patients suffering from post-herpeticneuralgia were not tolerated with a 0.025% capsaicin preparation(Zostrix, Gen Derm, USA). With a 0.075% preparation (Zostrix-HP, GenDerm, USA), 5 out of 16 (31.3%) and 45 out of 74 (60.8%) patients withpost-herpetic neuralgia were not tolerated (Peikert et al., 1991;Watanabe et al., 1994; Bernstein et al., 1989 and Watson et al., 1993).

Various capsaicin compositions have been developed over the years, inparticular, the psoriatic composition of U.S. Pat. No. 4,486,450, thenasal composition of U.S. Pat. No. 5,134,166, and the composition ofU.S. Pat. No. 4,997,853, the anti-inflammatory composition of U.S. Pat.No. 5,560,910, the composition of U.S. Pat. No. 5,962,532, thecomposition for animals of U.S. Pat. No. 5,916,565, the stomachtreatments of U.S. Pat. No. 5,889,041, the composition of U.S. Pat. No.5,827,886, the patch with medication of U.S. Pat. No. 5,741,510, all ofwhich are incorporated by reference herein.

U.S. Pat. No. 6,593,370 discloses a topical capsaicin preparation forthe treatment of painful cutaneous disorders and neural dysfunction. Thepreparation contains a nonionic, amphoteric or cationic surfactant in anamount effective to eliminate or substantially ameliorate burning paincaused by capsaicin.

U.S. Pat. No. 6,573,302 discloses a cream comprising: a topical carrierwherein the topical carrier comprises a member selected from the groupcomprising lavender oil, myristal myristate, and other preservativesincluding, hypericum perforatum arnica montana capric acid; and 0.01 to1.0 wt. % capsaicin; 2 to 10 wt. % an encapsulation agent selected fromthe group comprising colloidal oatmeal hydrogenated lecithin,dipotassium glycyrlhizinate and combinations thereof; esters of aminoacid; a light scattering element having a particle size up to 100 nm.;and a histidine.

U.S. Pat. No. 6,348,501 discloses a lotion for treating the symptoms ofarthritis using capsaicin and an analgesic, and a method for making.

U.S. Pat. No. 5,962,532 disclose methods and compositions for treatingpain at a specific site with an effective concentration of capsaicin oranalogues. The methods involve providing anesthesia to the site wherethe capsaicin or analogues thereof is to be administered, and thenadministering an effective concentration of capsaicin to the joint. Theanesthesia can be provided directly to the site, or at remote site thatcauses anesthesia at the site where the capsaicin is to be administered.For example, epidural regional anesthesia can be provided to patients towhich the capsaicin is to be administered at a site located from thewaist down. By pretreating the site with the anesthetic, a significantlyhigher concentration of capsaicin can be used. Effective concentrationsof capsaicin or analogues thereof range from between 0.01 and 10% byweight, preferably between 1 and 7.5% by weight, and more preferably,about 5% by weight. This provides for greater and more prolonged painrelief, for periods of time ranging from one week to several weeks. Insome cases the pain relief may be more sustained because the diseasethat underlies the pain may improve due to a variety of factorsincluding enhancement of physical therapy due to less pain in the softtissues which may foster enhanced mobilization of soft tissues, tendons,and joints.

U.S. Pat. No. 5,910,512 disclose a water-based topical analgesic andmethod of application wherein the analgesic contains capsicum, capsicumoleoresin and/or capsaicin. This analgesic is applied to the skin toprovide relief for rheumatoid arthritis, osteoarthritis, and the like.

U.S. Pat. No. 5,403,868 discloses novel capsaicin derivatives containingthio-urea, processes for the production thereof, pharmaceuticalcompositions containing them and use thereof as pharmaceuticals.

U.S. Pat. No. 5,178,879 discloses clear, water-washable, non-greasy gelsuseful for topical pain relief contain capsaicin, water, alcohol and acarboxypolymethylene emulsifier. A method of preparing the gels is alsodisclosed U.S. Pat. No. 5,021,450 relates to a new class of compoundshaving a variable spectrum of activities for capsaicin-like responses,compositions thereof, processes for preparing the same, and usesthereof. Compounds were prepared by combining phorbol relatedditerpenses and homovanillac acid analogs via esterification at theexocyclic hydroxy group of the diterpene. Examples of these compoundsinclude 20-homovanillyl-mezerein and20-homovanillyl-12-deoxyphorbol-13-phenylacetate.

U.S. Pat. No. 4,997,853 discloses a method and composition for treatingsuperficial pain syndromes which incorporates capsaicin in atherapeutically effective amount into a pharmaceutically acceptablecarrier and adding to this composition a local anesthetic such aslidocaine or benzocaine. The composition containing the anesthetic isthen applied to the site of the pain. A variation on the treatmentincludes initial treatment with the composition containing the localanesthetic until the patient has become desenstitized to the presence ofcapsaicin and subsequent treatment with a composition omitting the localanesthetic.

US application 20050019436 provides compositions and methods forrelieving pain at a site in a human or animal in need thereof byadministering at a discrete site in a human or animal in need thereof adose of capsaicin in an amount effective to denervate a discrete sitewithout eliciting an effect outside the discrete location, the dose ofcapsaicin ranging from 1 μg to 3000 μg.

US application 20040224037 claims a use of Capsaicin(8-methyl-n-vanillyl-6-nonenamide), its derivatives, vanilloids andcapsicum extract, to combat and control HIV (humans immunodeficiencyvirus) and AIDS (acquired immunodeficiency syndrome). An evaluation of acapsicum sp consumption of a long term aids survivors group permitted adefinition of more efficacious ways to administer the substance.capsaicin intravenous and by subcutaneous or intramuscularadministration at low concentration implemented by using infuses, itinhibits HIV replication and stimulates the production and proliferationof lymphocytes and cells NK. Also it acts as disinfectant inmacrophages, and has a power as anticancer and antioxidant agent.Moreover has the property to control and annihilate common opportunisticillnesses related to HIV due to its triple antibiotic characteristics.

US application 20040146590 provides methods and kits for the selectiveablation of pain-sensing neurons. The methods comprise administration ofa vanilloid receptor agonist to a ganglion in an amount that causesdeath of vanilloid receptor-bearing neurons. Accordingly, the presentinvention provides methods of controlling pain and inflammatorydisorders that involve activation of vanilloid receptor-bearing neurons.

US application 20030133995 discloses a chemical composition for aningestible capsaicin neutralizer to neutralize the effect of capsaicinon the oral cavity, tongue, and esophagus when capsaicin from hotpeppers is ingested by a user comprised of an effective neutralizingamount of casein protein, or the salt thereof, an alkali earth metalhalide, and the balance water.

US application 20030082249 discloses a composition for use in treatingor preventing mucositis, and/or xerostomia, including capsaicin orcapsaicin derivative, and one or more additional compounds useful intreating mucositis and/or xerostomia, wherein the composition isprovided in an oral delivery vehicle. The term capsaicin derivative andcapsaicinoid as used in the disclosure are interchangeable and generallyrefer to capsaicin analogs. Among the capsaicinoids useful in thepractice of the disclosure are capsaicin, the N-phenylmethylalkenamidecapsaicin derivatives; dihydrocapsaicin; norhydrocapsaicin;nordihydrocapsaicin; homocapsaicin; homohydrocapsaicin;homodihydrocapsaicin; civamide (cis-capsaicin); nonivamide; NE-19550(N-[4-hydroxy-3-methoxyphenyl)methyl-1]-9Z-octadecanamide) (olvanil);NE-21610(N-[(4-(2-aminoethoxy)-3-methoxyphenyl)methyl]-9Z-octadecanamide) SandozPharmaceutical Corp, East Hanover, N.J.); NE-28345(N-(9Z-octadecenyl)-3-methoxy-4-hydroxyphenylacetamide; also known asN-oleyl-homovanillamide); and their analogs and derivatives (U.S. Pat.No. 5,762,963, which is incorporated herein by reference). NE-19550,NE-21610, and NE-28345 are discussed in Dray et al. (1990).

US application 20020058048 discloses a topical capsaicin preparation forthe treatment of painful cutaneous disorders and neural dysfunction isdisclosed. The preparation contains a nonionic, amphoteric or cationicsurfactant in an amount effective to eliminate or substantiallyameliorate burning pain caused by capsaicin.

US application 20010002406 discloses transdermal application ofcapsaicin (or a capsaicin analog) in a concentration from greater thanabout 5% to about 10% by weight to be an extremely effective therapy fortreating neuropathic pain, so long as an anesthetic, preferably by meansof a transdermal patch, is administered initially to the affected areato minimize the expected side effects from subsequent capsaicinapplication. Analogs of capsaicin with physiological properties similarto capsaicin are known (Ton 1955). For example, resiniferatoxin isdescribed as a capsaicin analog by Blumberg, U.S. Pat. No. 5,290,816.U.S. Pat. No. 4,812,446, describes capsaicin analogs and methods fortheir preparation.

U.S. Pat. Nos. 4,493,848 and 4,564,633 disclose the derivatives ofcapsaicin, including short chain ester derivatives (C1-C6) of capsaicinfor analgesia in human.

Cetyl myristoleate (CMO) is the common name for cis-9-cetyl myristoleateand the structure of cetyl myristoleate is shown in FIG. 3. In 1972Diehl (1994) discovered that Swiss albino mice did not get arthritisafter injection of Freund's adjuvant. Eventually, he was able todetermine that cetyl myristoleate was the factor present naturally inmice which was responsible for this protection. When cetyl myristoleatewas injected into various strains of rats, it offered the sameprotection against arthritis. Cetyl myristoleate is a natural mediumchain fatty acid found in certain animals, including cows, whales,beavers, and mice. It has been proposed that cetyl myristoleate acts asa joint “lubricant” and anti-inflammatory agent.

The rational for the use of cetyl myristoleate is that it may inhibitthe production of inflammatory prostaglandins and leukotrienes. Theprocess of inflammation involves the release of proinflammatorycytokines (e.g., interleukin 1β and tumor necrosis factor-α). Fattyacids, especially n-6 fatty acids, have been proposed to reduce chronicinflammation in patients with rheumatoid arthritis by reducingleukotriene B4 from stimulated neutrophils and of interleukin-1monocytes (Kremer 2000; 1996). In addition, other suggested mechanismsfor the anti-inflammatory response observed with fatty acid treatmentare reduced expression and activity of proteoglycan degrading enzymesand cytokines, suppression of leukocyte function, changes in adhesionmolecule expression and apoptosis triggering, and alterations in signaltransduction and membrane fluidity (Kremer 2000; Curtis 2000 and Heraud2000).

U.S. Pat. Nos. 5,569,676, 4,113,881 and 4,049,824 disclose the use ofcetyl myristoleate in both osteoarthritis and rheumatoid arthritis andseveral scientific studies have documented the benefit of cetylmyristoleate in relieving pain based upon the animal studies and severalcase histories (Siemendi 1997; Cochran 1996; Elkins 1997 and Hesslink2002). In a double-blind study, 106 individuals with various types ofarthritis who had failed to respond to non-steroidal anti-inflammatorydrugs received cetyl myristoleate (540 mg per day orally for 30 days),while 226 others received a placebo. These individuals also appliedcetyl myristoleate or placebo topically, according to their perceivedneed. Some 63.5% of those receiving cetyl myristoleate improved,compared with only 14.5% of those receiving the placebo (Siemandi 1997and Cochran 1996).

A need exists for a topical preparation which eliminates orsubstantially ameliorates initial stinging pain caused by capsaicinobserved in the administration with anti-inflammatory properties therebymaking the preparation tolerable in long-term administration.

The purpose of the present application is to disclose the unexpecteddiscovery that esters of capsaicin have significantly less burning painat the site of the application and the synergistic combination of theesters of capsaicin and esters of myristoleic acid are extremelyeffective in treating pain in humans. The present invention does notrely on topical anesthetics, such as lidocaine (Entry 5310, p. 786 MerckIndex, Tenth Edition 1983) and benzocaine (ethyl aminobenzoate, Entry3710, p. 546 Merck Index, Tenth Edition, 1983) into formulationscontaining capsaicin, and then applying such formulations for theinitial period of treatment to eliminate the painful burning from theapplication of capsaicin, allowing the patient to continue therapy whilebeing able to feel through the skin onto which the cream is applied.

SUMMARY OF THE INVENTION

The present invention provides for certain novel pharmaceuticalcompositions containing synergistic combination of ester derivatives ofcapsaicin and ester derivatives of myristoleic acid that are highlylipophilic. The compounds of capsaicin and myristoleic acid set forthherein are enzymatically cleaved to the parent compound. Thus, thecompounds set forth herein provide for a novel form of therapy ofdiseases amendable to treatment with capsaicin and myristoleic acid.

The synergistic combination of the ester derivatives of capsaicin andthe ester of myristoleic acid of the present invention would havesignificant utility over capsaicin and existing derivatives currentlydescribed in the patent and scientific literature. In particular, inview of their high lipophilicity, non-irritation to the skin,significantly less burning sensation at the site of application andstability, these new derivatives would be more bioavailable whenadministered topically compared to capsaicin. In addition, because oftheir stability and non-toxic nature, these agents can be made morereadily available to the general public. The inventors have surprisinglyand unexpectedly discovered that the ester derivatives of capsaicin incombination with the esters of myristoleic acid have therapeutic utilityin treating pain in humans. These compounds thus provide for a novelform of therapy of any disease or condition wherein capsaicin andmyristoleic acid are believed to be of benefit, including but notlimited to, post-herpetic neuralgia, shingles (herpes zoster), diabeticneuropathy, postmastectomy pain syndrome, oral neuropathic pain,trigeminal neuralgia, temperomandibular joint disorders, pruritus,cluster headache, osteoarthritis, arthritis pain, rhinopathy, oralmucositis, cutaneous allergy, detrusor hyperreflexia, loinpain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

The present invention generally pertains to pharmaceutical compositionscontaining a compound of formula (Ia):R—CO-CAP  (Ia)wherein CAP refers to collectively the capsaicins represented in FIG. 1and a compound of formula (Ib):MCO-O—R  (Ib)wherein MCO refers to myristoleic acid represented in FIG. 3.

In formulae Ia and Ib, R is selected from alkyl groups of up to about 18carbon atoms and aryl groups of up to about 18 carbon atoms and alkylenegroup of up to about 18 carbon atoms and an arylene group of up to about18 carbon atoms. The alkyl, aryl and alkylene groups may be substitutedor unsubstituted, branched or straight chains. In addition, R maycontain heteroatoms and may be straight chained or branched.

Examples of suitable straight-chain alkyl groups in formula Ia and Ibinclude methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, dodecyl,1-pentadecyl, 1-heptadecyl, 1-hexadecyl, 1-octadecyl and the likegroups.

Examples of suitable branched chain alkyl groups in formula Ia and Ibinclude isopropyl, sec-butyl, t-butyl, 2-methylbutyl, 2-pentyl, 3-pentyland the like groups.

Examples of suitable cyclic alkyl groups in formula Ia and Ib includecyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl groups.

Examples of suitable “alkenyl” groups in formula Ia and Ib include vinyl(ethenyl), 1-propenyl, i-butenyl, pentenyl, hexenyl, n-decenyl andc-pentenyl and the like.

The groups may be substituted, generally with 1 or 2 substituents,wherein the substituents are independently selected from halo, hydroxy,alkoxy, amino, mono- and dialkylamino, nitro, carboxyl, alkoxycarbonyl,and cyano groups.

By the expression “phenalkyl groups wherein the alkyl moiety contains 1to 3 or more carbon atoms” is meant benzyl, phenethyl and phenylpropylgroups wherein the phenyl moiety may be substituted. When substituted,the phenyl moiety of the phenalkyl group may contain independently from1 to 3 or more alkyl, hydroxy, alkoxy, halo, amino, mono- anddialkylamino, nitro, carboxyl, alkoxycarbonyl and cyano groups.

Examples of suitable “heteroaryl” in formula Ia and Ib are pyridinyl,thienyl or imidazolyl.

As noted herein, the expression “halo” is meant in the conventionalsense to include F, Cl, Br, and I.

Among the compounds represented by the general Formula Ia and Ib,preferred compounds are such in which R is one of the following groups:methyl, ethyl, propyl, butyl, pentyl, hexyl, 1-pentadecyl, 1-heptadecyl,1-hexadecyl, 1-octadecyl, isobutyl, methoxyethyl, ethoxyethyl, benzyland nicotinyl.

The compounds of Formula Ia are esters of capsacin and its analogues andcompounds of Ib are esters of myristoleic acid. However, information inthe literature does not disclose or indicate the esters of capsaicinhave any utility as pro-drug forms in combination with the esters ofmyristoleic acid suitable for oral and topical delivery for treatingdiseases such as post-herpetic neuralgia, shingles (herpes zoster),diabetic neuropathy, postmastectomy pain syndrome, oral neuropathicpain, trigeminal neuralgia, temperomandibular joint disorders, pruritus,cluster headache, osteoarthritis, arthritis pain, rhinopathy, oralmucositis, cutaneous allergy, detrusor hyperreflexia, loinpain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

The present invention also generally pertains to pharmaceuticalcompositions comprising one or more of the compounds set forth above.

Accordingly, one aspect of the present invention is to disclose thecombination of esters of capsaicin and esters of myristoleic acid in thetreatment of post-herpetic neuralgia, shingles (herpes zoster), diabeticneuropathy, postmastectomy pain syndrome, oral neuropathic pain,trigeminal neuralgia, temperomandibular joint disorders, pruritus,cluster headache, osteoarthritis, arthritis pain, rhinopathy, oralmucositis, cutaneous allergy, detrusor hyperreflexia, loinpain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

In particular, the esters of capsaicin and esters of myristoleic aciddescribed herein may be used for the preparation of therapeuticcompositions in the treatment of post-herpetic neuralgia, shingles(herpes zoster), diabetic neuropathy, postmastectomy pain syndrome, oralneuropathic pain, trigeminal neuralgia, temperomandibular jointdisorders, pruritus, cluster headache, osteoarthritis, arthritis pain,rhinopathy, oral mucositis, cutaneous allergy, detrusor hyperreflexia,loin pain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor in humans.

Preferably, the compositions useful in the method may be topicallyapplied to the human in need of such therapy.

The method of the present invention neither destroys healthy, uninfectedtissue nor results in any local or systemic side effects, scarring,disfigurement or discomfort to the human treated. Furthermore, the useof the esters of the present invention reduces the occurrence of skinirritation and rashes unlike the free capsaicin. The method includes theuse of ester of capsaicin and ester of myristoleic acid for theadministration to an area of the human which is anticipated to evidence,post-herpetic neuralgia, shingles (herpes zoster), diabetic neuropathy,postmastectomy pain syndrome, oral neuropathic pain, trigeminalneuralgia, temperomandibular joint disorders, pruritus, clusterheadache, osteoarthritis, arthritis pain, rhinopathy, oral mucositis,cutaneous allergy, detrusor hyperreflexia, loin pain/hematuria syndrome,neck pain, amputation stump pain, reflex sympathetic dystrophy and paindue to skin tumor.

In accordance with the method according to this invention, regular useof the esters of capsaicin and esters of myristoleic acid is meant tomean application of the esters of capsaicin and esters of myristoleicacid at least once a day to the body surface containing post-herpeticneuralgia, shingles (herpes zoster), diabetic neuropathy, postmastectomypain syndrome, oral neuropathic pain, trigeminal neuralgia,temperomandibular joint disorders, pruritus, cluster headache,osteoarthritis, arthritis pain, rhinopathy, oral mucositis, cutaneousallergy, detrusor hyperreflexia, loin pain/hematuria syndrome, neckpain, amputation stump pain, reflex sympathetic dystrophy and pain dueto skin tumor.

There is further disclosed a method for the treatment of post-herpeticneuralgia, shingles (herpes zoster), diabetic neuropathy, postmastectomypain syndrome, oral neuropathic pain, trigeminal neuralgia,temperomandibular joint disorders, pruritus, cluster headache,osteoarthritis, arthritis pain, rhinopathy, oral mucositis, cutaneousallergy, detrusor hyperreflexia, loin pain/hematuria syndrome, neckpain, amputation stump pain, reflex sympathetic dystrophy and pain dueto skin tumor, comprising the application of a cream or douchecontaining either an ester of capsaicin or mixtures thereof and eitheran ester of myristoleic acid or mixtures thereof, to the affected areaof the human body.

There is also disclosed a method for treating post-herpetic neuralgia,shingles (herpes zoster), diabetic neuropathy, postmastectomy painsyndrome, oral neuropathic pain, trigeminal neuralgia, temperomandibularjoint disorders, pruritus, cluster headache, osteoarthritis, arthritispain, rhinopathy, oral mucositis, cutaneous allergy, detrusorhyperreflexia, loin pain/hematuria syndrome, neck pain, amputation stumppain, reflex sympathetic dystrophy and pain due to skin tumor, saidmethod comprising the application of either an ester of capsaicin ormixtures thereof and either an ester of myristoleic acid or mixturesthereof, to the affected area of a human for a period of time and at asufficient concentration to eradicate symptoms in the human.

The pharmaceutical compositions of the present invention canadditionally include one or more pharmaceutically acceptable excipients.One of ordinary skill in the art would be familiar with pharmaceuticallyacceptable excipients. For example, the pharmaceutically acceptableexcipient may be a water soluble sugar, such as mannitol, sorbitol,fructose, glucose, lactose, and sucrose.

The pharmaceutical compositions of the present invention may furthercomprise one or more pharmaceutically acceptable antioxidants. Anypharmaceutically acceptable antioxidant known to those of ordinary skillin the art is contemplated for inclusion in the present pharmaceuticalcompositions. For example, the pharmaceutically acceptable antioxidantmay be selected from the group consisting of ascorbic acid, sodiumascorbate, sodium bisulfate, sodium metabisulfate and monothio glycerol.

The pharmaceutical compositions of the present invention may furthercomprise one or more pharmaceutically acceptable preservatives. Anypharmaceutically acceptable preservative known to those of ordinaryskill in the art is contemplated for inclusion in the presentpharmaceutical compositions. Examples of such preservatives includemethylparaben, methylparaben sodium, propylparaben, propylparabensodium, benzalkonium chloride, and benzethonium chloride.

The pharmaceutical compositions of the present invention may furthercomprise one or more pharmaceutically acceptable buffering agents. Anypharmaceutically acceptable buffering agent known to those of ordinaryskill in the art is contemplated for inclusion in the presentpharmaceutical compositions. Examples of such buffering agents includeof monobasic sodium phosphate, dibasic sodium phosphate, sodiumbenzoate, potassium benzoate, sodium citrate, sodium acetate, and sodiumtartrate.

The pharmaceutical compositions of the present invention can include anyconcentration of a compound of the present invention. For example, theconcentration of compound may be 0.1 mg/ml to 1000 mg/ml or greater. Incertain particular embodiments, the concentration of compound is 1 mg/mlto 500 mg/ml. In still further embodiments, the concentration ofcompound is 5 mg/ml to 100 mg/ml.

In some embodiments of the present invention, the pharmaceuticalcomposition includes more than one of the novel compounds set forthabove. In other embodiments of the present invention, the pharmaceuticalcomposition includes one or more secondary therapeutic agents directedto a disease or health-related condition, as discussed below.

The present invention also generally pertains to methods of treating orpreventing a pathological condition in a subject, comprising providing atherapeutically effective amount of any of the pharmaceuticalcompositions set forth above, and administering the composition to thesubject. The subject can be any subject, such as a mammal or avianspecies. In certain particular embodiments, the mammal is a human. Thehuman may be an individual affected by or at risk of developing adisease or condition amenable to therapy with capsaicin. For example,the pathological condition may be post-herpetic neuralgia, shingles(herpes zoster), diabetic neuropathy, postmastectomy pain syndrome, oralneuropathic pain, trigeminal neuralgia, temperomandibular jointdisorders, pruritus, cluster headache, osteoarthritis, arthritis pain,rhinopathy, oral mucositis, cutaneous allergy, detrusor hyperreflexia,loin pain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

The pharmaceutical composition of the present invention may beadministered to the subject by any method known to those of ordinaryskill in the art. For example, the method of administering thecomposition to the subject may include oral, topical, nasal,inhalational, rectal, or vaginal. Methods of administration arediscussed in greater detail in the specification below.

In certain embodiments of the methods of the present invention, themethod involves administering to the subject a therapeutically effectiveamount of a secondary agent. The secondary agent can be anypharmacologic agent known or suspected to be of benefit in the treatmentor prevention of a disease or health-related condition in a subject. Forexample, in some embodiments, the secondary agent is a secondary painrelieving agent. Secondary pain relieving agents, which includemorphine, are well-known to those of ordinary skill in the art. Examplesof such agents include aspirin, acetaminophen (Tylenol) or otheraspirin-like drugs called nonsteroidal anti-inflammatory drugs (NSAIDs),weak narcotics such as codeine (Tylenol with codeine), hydrocodone(Vicodin or Lortab), Percocet, Percodan or propoxyphene (Darvon), strongopioids such as morphine, Demerol, Dilaudid, fentanyl (duragesicpatches) and methadone.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein.

FIG. 1. is a picture of the chemical structures of capsaicins.

FIG. 2. is a picture of the formula of the chemical structures ofcapsaicin esters.

FIG. 3. Is a picture of the formula of the chemical structures ofmyristoleic acid esters.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is based on the inventors' discovery of certainpharmaceutical compositions containing esters of myristoleic acid andderivatives of capsaicin that are highly lipophilic, non-irritating, andthus allow higher concentrations for improved bioavailability followingadministration in a cream or ointment formulations. The pharmaceuticalcompositions of the present invention include esters of capsaicin andesters of myristoleic acid. These compounds are suitable by any route ofadministration, but are particularly suited for oral or topicaladministration in view of their lipid solubility. These pharmaceuticalcompositions thus provide for a novel form of therapy of any disease orcondition wherein capsaicin or myristoleic acid is believed to be ofbenefit, post-herpetic neuralgia, shingles (herpes zoster), diabeticneuropathy, post-mastectomy pain syndrome, oral neuropathic pain,trigeminal neuralgia, temperomandibular joint disorders, pruritus,cluster headache, osteoarthritis, arthritis pain, rhinopathy, oralmucositis, cutaneous allergy, detrusor hyperreflexia, loinpain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

DETAILED DESCRIPTION OF THE INVENTION A. Capsaicin Derivatives of thePresent Invention

Before describing the present invention in detail, it is to beunderstood that this invention is not limited to particular drugs ordrug delivery systems, as such may vary. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only, and is not intended to be limiting.

It must be noted that, as used in this specification, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a pharmacologicallyactive agent” includes a combination of two or more pharmacologicallyactive agents, and the like. In describing the present invention, thefollowing terminology will be used in accordance with the definitionsset out below.

As used herein in the claim(s), when used in conjunction with the word“comprising”, the words “a” or “an” may mean one or more than one. Asused herein “another” may mean at least a second or more.

The terms “active agent,” “drug” and “pharmacologically active agent”are used interchangeably herein to refer to a chemical material orcompound which, when administered to an organism (human or animal)induces a desired pharmacologic effect. Included are derivatives andanalogs of those compounds or classes of compounds specificallymentioned which also induce the desired pharmacologic effect.

The term “topical administration” is used in its conventional sense tomean delivery of a topical drug or pharmacologically active agent to theskin or mucosa.

“Carriers” or “vehicles” as used herein refer to carrier materialssuitable for drug administration. Carriers and vehicles useful hereininclude any such materials known in the art, e.g., any liquid, gel,solvent, liquid diluent, solubilizer, or the like, which is nontoxic andwhich does not interact with other components of the composition in adeleterious manner.

By an “effective” amount of a drug or pharmacologically active agent ismeant a nontoxic but sufficient amount of the drug or agent to providethe desired effect.

The term “capsaicin or capsaicins” as used herein is intended toencompass not only the compound capsaicin, but also homocapsaicin,nordihydrocapsaicin, dihydrocapsaicin, homodihydrocapsaicin or anycompounded mixture thereof (see FIG. 1).

The present invention provides for certain novel pharmaceuticalcompositions containing ester derivatives of capsaicin and esterderivatives of myristoleic acid that are highly lipophilic. The ester ofcapsaicin and the ester of myristoleic acid set forth herein areenzymatically cleaved to the parent compound. Thus, the pharmaceuticalcompositions set forth herein provide for a novel form of therapy ofdiseases amendable to treatment with capsaicin and esters of myristoleicacid.

The combination of the ester derivatives of capsaicin and the ester ofmyristoleic acid of the present invention would have significant utilityover capsaicin or myristoleic acid and existing derivatives currentlydescribed in the patent and scientific literature. In particular, inview of their high lipophilicity, non-irritation to the skin,significantly less burning sensation at the site of application andstability, these derivatives would be more bioavailable whenadministered topically compared to capsaicin or myristoleic acid. Inaddition, because of their stability and non-toxic nature, these agentscan be made more readily available to the general public.

The inventors have surprisingly and unexpectedly discovered that theester derivatives of capsaicin in combination with the esters ofmyristoleic acid have therapeutic utility in treating pain in humans.These compositions thus provide for a novel form of therapy of anydisease or condition wherein capsaicin or myristoleic acid is believedto be of benefit, including but not limited to, post-herpetic neuralgia,shingles (herpes zoster), diabetic neuropathy, postmastectomy painsyndrome, oral neuropathic pain, trigeminal neuralgia, temperomandibularjoint disorders, pruritus, cluster headache, osteoarthritis, arthritispain, rhinopathy, oral mucositis, cutaneous allergy, detrusorhyperreflexia, loin pain/hematuria syndrome, neck pain, amputation stumppain, reflex sympathetic dystrophy and pain due to skin tumor.

The present invention generally pertains to pharmaceutical compositionscontaining a compound of formula (Ia):R—CO-CAP  (Ia)wherein CAP refers to collectively the capsaicins represented in FIG. 1and a compound of formula (Ib):MCO-O—R  (Ib)Wherein MCO refers to myristoleic acid represented in FIG. 3.

In formula Ia and Ib, R is selected from alkyl groups of up to about 18carbon atoms and aryl groups of up to about 18 carbon atoms and alkylenegroup of up to about 18 carbon atoms and an arylene group of up to about18 carbon atoms. The alkyl, aryl and alkylene groups may be substitutedor unsubstituted, branched or straight chains. In addition, R maycontain heteroatoms and may be straight chained or branched.

Examples of suitable straight-chain alkyl groups in formula Ia and Ibinclude methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, dodecyl,1-pentadecyl, 1-heptadecyl 1-hexadecyl, 1-octadecyl and the like groups.

Examples of suitable branched chain alkyl groups in formula I includeisopropyl, sec-butyl, t-butyl, 2-methylbutyl, 2-pentyl, 3-pentyl and thelike groups.

Examples of suitable cyclic alkyl groups in formula Ia and Ib includecyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl groups.

Examples of suitable “alkenyl” groups in Ia and Ib include vinyl(ethenyl), 1-propenyl, i-butenyl, pentenyl, hexenyl, n-decenyl andc-pentenyl and the like.

The groups may be substituted, generally with 1 or 2 substituents,wherein the substituents are independently selected from halo, hydroxy,alkoxy, amino, mono- and dialkylamino, nitro, carboxyl, alkoxycarbonyl,and cyano groups.

By the expression “phenalkyl groups wherein the alkyl moiety contains 1to 3 or more carbon atoms” is meant benzyl, phenethyl and phenylpropylgroups wherein the phenyl moiety may be substituted. When substituted,the phenyl moiety of the phenalkyl group may contain independently from1 to 3 or more alkyl, hydroxy, alkoxy, halo, amino, mono- anddialkylamino, nitro, carboxyl, alkoxycarbonyl and cyano groups.

Examples of suitable “heteroaryl” in formula Ia and Ib are pyridinyl,thienyl or imidazolyl.

As noted herein, the expression “halo” is meant in the conventionalsense to include F, Cl, Br, and I.

Among the compounds represented by the general Formula Ia and Ib,preferred compounds are such in which R is one of the following groups:methyl, ethyl, propyl, butyl, pentyl, hexyl, 1-pentadecyl, 1-heptadecyl,1-hexadecyl, 1-octadecyl, isobutyl, methoxyethyl, ethoxyethyl, benzyland nicotinyl.

The compounds of Formula Ia are esters of capsacin and its analogues andcompounds of Ib are esters of myristoleic acid. However, information inthe literature do not disclose or indicate the esters of capsaicin haveany utility as pro-drug forms in combination with the esters ofmyristoleic acid suitable for oral and topical delivery for treatingdiseases such as post-herpetic neuralgia, shingles (herpes zoster),diabetic neuropathy, postmastectomy pain syndrome, oral neuropathicpain, trigeminal neuralgia, temperomandibular joint disorders, pruritus,cluster headache, osteoarthritis, arthritis pain, rhinopathy, oralmucositis, cutaneous allergy, detrusor hyperreflexia, loinpain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

B. Methods of Synthesis

The compounds used in the present invention can be prepared by anymethod known to those of ordinary skill in the art. For example, theesters of myrisoleic acid can be obtained commercially as oil, powder orwax (EHP Products Inc, USA). Various methods have been described in theliterature pertaining to the synthesis of a number of esters ofcarboxylic acids and phenols (March's Advanced Organic Chemistry:Reactions, Mechanisms, and Structure, 5th Edition, by Michael B. Smithand Jerry March, John Wiley and Sons, Inc, 2001).

One method that has been utilized for efficient preparation of the esterof capsaicin of the present invention is through dissolution of thecompound in methylene dichloride. Since capsaicin USP27 contains >95% ofcapsaicins, to this solution slightly in excess of 1.1 mole equivalentof anhydrous triethylamine is added with stirring at room temperature.To this solution slightly in excess of 1 mole equivalent of an acidchloride is added with stirring while keeping the temperature around 25°C. After that, the solution was refluxed for 2-5 hours and stirred for12-17 hours at room temperature. The reaction mixture was then washedwith equal amount of water three to four times to remove the unreactedamine and its salt in a separating funnel. The organic phase was washed3-4 times with dilute hydrochloric acid solution in a separating funnelto remove any amine present in the organic solution. The reactionmixture was then washed with equal amount of 10% sodium carbonatesolution three to four times to remove the unreacted acid and salts in aseparating funnel. The reaction mixture was then washed with equalamount of water three to four times in a separating funnel. The organicphase was dried with anhydrous sodium sulfate overnight and themethylene dichloride was removed in a rotary evaporator under vacuum.The resultant oily or vaxy material is called the ester capsaicin as allof the phenols present capsaicin is converted into the correspondingester.

C. Pharmaceutical Compositions

Certain embodiments of the present invention pertain to pharmaceuticalcompositions comprising the esters of capsaicins and esters ofmyristoleic acid set forth herein.

The phrases “pharmaceutical,” “pharmaceutically,” or “pharmacologicallyacceptable” refer to molecular entities and compositions that do notproduce an unacceptably adverse, allergic or other untoward reactionwhen administered to an animal, or human, as appropriate. As usedherein, “pharmaceutical” includes any and all solvents, dispersionmedia, coatings, antibacterial and antifungal agents, isotonic andabsorption delaying agents and the like. The use of such media andagents for pharmaceutical active substances is well known in the art.Except insofar as any conventional media or agent is incompatible withthe active ingredients, its use in the therapeutic compositions iscontemplated. Supplementary active ingredients to treat the disease ofinterest, such as other anti-cancer agents or anti-inflammatory agents,can also be incorporated into the compositions.

Pharmaceutical compositions of the present invention will include aneffective amount of one or more of the ester derivatives of capsaicinand the ester derivatives of myristoleic acid set forth herein that areclinically determined to be useful in the treatment of the particulardisease under consideration. One of ordinary skill in the art would befamiliar with what type of dosage is required for treatment of theparticular pathological condition that is present in the subject. Noundue experimentation would be involved. When used for therapy, thecompositions of the present invention are administered to subjects intherapeutically effective amounts. For example, an effective amount ofthe ester of capsaicin in a patient with diabetic neuropathy may be anamount that promotes the healing of the pain associated with theneuropathy. The dose will depend on the nature of the disease, thesubject, the subject's history, and other factors. Preparation of suchcompositions is discussed in other parts of this specification.

As discussed above, the derivatives of capsaicin set forth herein havegreater lipophilicity and significantly less irritation to the skin thancapsaicin. One advantage of these esters is that they can beincorporated into a cream or ointment form at a higher percentage byweight as compared to capsaicin. Another advantage is that thesecompositions have a very low toxicity and irritation to the skin ascompared to formulations of capsaicin.

The compositions of the capsaicin derivatives and myristoleic acidderivatives of the present invention can be delivered by any methodknown to those of ordinary skill in the art. For example, thepharmaceutical compositions can be delivered by topical or oral deliveryroutes.

Compositions employing the esters of capsaicin and esters of myristoleicacid set forth herein will contain a biologically effective amount ofthe derivative. As used herein a biologically effective amount of acompound or composition refers to an amount effective to alter, modulateor reduce disease conditions. One of ordinary skill in the art would befamiliar with methods of determining a biologically effective amount ofa therapeutic agent. For example, a biologically effective amount may beabout 0.1 mg/kg to about 50 mg/kg or greater

The therapeutic combination of esters of capsaicin and esters ofmyristoleic acid of the present invention may be administered alone orin combination with one or more additional therapeutic esters of thepresent invention. In other embodiments, the therapeutic combination ofester of capsaicin and ester of myristoleic acid is administered incombination with one or more secondary forms of therapy directed to thedisease or condition to be treated. These are discussed in greaterdetail below. Additional pharmaceutical compounds may be administered inthe same pharmaceutical composition, or in a separate dosage form, suchas in a separate oral, intramuscular, or intravenous dosage forms takenat the same time.

The therapeutic agents of the present invention may be supplied in anyform known to those of ordinary skill in the art. For example, thetherapeutic agent may be supplied as a liquid or as a solution. Thepharmaceutical compositions may contain a preservative to prevent thegrowth of microorganisms. It must be chemically and physically stableunder the conditions of manufacture and storage and must be preservedagainst the contaminating action of microorganisms, such as bacteria andfungi. The prevention of the action of microorganisms can be broughtabout by various antibacterial and antifungal agents, for example,parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like.

The formulations according to the invention having been described hereinmay influence the ordinarily skilled artesian to make similarformulations using components that will be known in the art, withoutdeparting from the invention which is claimed herein.

The pharmaceutical formulations of the esters of capsaicin and esters ofmyristoleic acid according to the present invention offer severaladvantages over the existing formulations. They can be topically appliedand relatively high concentrations of the esters of capsaicin can beloaded into patients with high bioavailability. Thus the frequency ofdosage can be reduced. Thus within the spirit, the invention is relatedto improved formulations and methods of using the same whenadministering such formulations to patients. As mentioned herein above anumber of excipients may be appropriate for use in the formulation whichcomprises the composition according to the present invention. Theinclusion of excipients and the optimization of their concentration fortheir characteristics such as for example ease of handling or carrieragents will be understood by those ordinarily skilled in the art not todepart from the spirit of the invention as described herein and claimedherein below.

Following preparation of the pharmaceutical compositions of the presentinvention, it may be desirable to quantify the amount of the esters ofcapsaicin and esters of myristoleic acid in the pharmaceuticalcomposition. Methods of measuring concentration of a drug in acomposition include numerous techniques that are well-known to those ofskill in the art. Selected examples include chromatographic techniques.There are many kinds of chromatography which may be used in the presentinvention: drug-specific assays, adsorption, partition, ion-exchange andmolecular sieve, and many specialized techniques for using themincluding column, paper, thin-layer chromatography, gas chromatography,and high performance liquid chromatography (HPLC). One of ordinary skillin the art would be familiar with these and other related techniques.

D. Moisturizing Agents

Certain topical formulations of the present invention may containmoisturizing agents. Non-limiting examples of moisturizing agents thatcan be used with the compositions of the present invention include aminoacids, chondroitin sulfate, diglycerin, erythritol, fructose, glucose,glycerin, glycerol polymers, glycol, 1,2,6-hexanetriol, honey,hyaluronic acid, hydrogenated honey, hydrogenated starch hydrolysate,inositol, lactitol, maltitol, maltose, mannitol, natural moisturizationfactor, PEG-15 butanediol, polyglyceryl sorbitol, salts of pyrollidonecarboxylic acid, potassium PCA, propylene glycol, sodium glucuronate,sodium PCA, sorbitol, sucrose, trehalose, urea, and xylitol.

Other examples include acetylated lanolin, acetylated lanolin alcohol,acrylates/C10-30 alkyl acrylate crosspolymer, acrylates copolymer,alanine, algae extract, aloe barbadensis, aloe-barbadensis extract, aloebarbadensis gel, althea officinalis extract, aluminum starchoctenylsuccinate, aluminum stearate, apricot (prunus armeniaca) kerneloil, arginine, arginine aspartate, arnica montana extract, ascorbicacid, ascorbyl palmitate, aspartic acid, avocado (persea gratissima)oil, barium sulfate, barrier sphingolipids, butyl alcohol, beeswax,behenyl alcohol, beta-sitosterol, BHT, birch (betula alba) bark extract,borage (borago officinalis) extract, 2-bromo-2-nitropropane-1,3-diol,butcherbroom (ruscus aculeatus) extract, butylene glycol, calendulaofficinalis extract, calendula officinalis oil, candelilla (euphorbiacerifera) wax, canola oil, caprylic/capric triglyceride, cardamon(elettaria cardamomum) oil, carnauba (copernicia cerifera) wax,carrageenan (chondrus crispus), carrot (daucus carota sativa) oil,castor (ricinus communis) oil, ceramides, ceresin, ceteareth-5,ceteareth-12, ceteareth-20, cetearyl octanoate, ceteth-20, ceteth-24,cetyl acetate, cetyl octanoate, cetyl palmitate, chamomile (anthemisnobilis) oil, cholesterol, cholesterol esters, cholesterylhydroxystearate, citric acid, clary (salvia sclarea) oil, cocoa(theobroma cacao) butter, coco-caprylate/caprate, coconut (cocosnucifera) oil, collagen, collagen amino acids, corn (zea mays) oil,fatty acids, decyl oleate, dextrin, diazolidinyl urea, dimethiconecopolyol, dimethiconol, dioctyl adipate, dioctyl succinate,dipentaerythrityl hexacaprylate/hexacaprate, DMDM hydantoin, DNA,erythritol, ethoxydiglycol, ethyl linoleate, eucalyptus globulus oil,evening primrose (oenothera biennis) oil, fatty acids, tructose,gelatin, geranium maculatum oil, glucosamine, glucose glutamate,glutamic acid, glycereth-26, glycerin, glycerol, glyceryl distearate,glyceryl hydroxystearate, glyceryl laurate, glyceryl linoleate, glycerylmyristate, glyceryl oleate, glyceryl stearate, glyceryl stearate SE,glycine, glycol stearate, glycol stearate SE, glycosaminoglycans, grape(vitis vinifera) seed oil, hazel (corylus americana) nut oil, hazel(corylus avellana) nut oil, hexylene glycol, honey, hyaluronic acid,hybrid safflower (carthamus tinctorius) oil, hydrogenated castor oil,hydrogenated coco-glycerides, hydrogenated coconut oil, hydrogenatedlanolin, hydrogenated lecithin, hydrogenated palm glyceride,hydrogenated palm kernel oil, hydrogenated soybean oil, hydrogenatedtallow glyceride, hydrogenated vegetable oil, hydrolyzed collagen,hydrolyzed elastin, hydrolyzed glycosaminoglycans, hydrolyzed keratin,hydrolyzed soy protein, hydroxylated lanolin, hydroxyproline,imidazolidinyl urea, iodopropynyl butylcarbamate, isocetyl stearate,isocetyl stearoyl stearate, isodecyl oleate, isopropyl isostearate,isopropyl lanolate, isopropyl myristate, isopropyl palmitate, isopropylstearate, isostearamide DEA, isostearic acid, isostearyl lactate,isostearyl neopentanoate, jasmine (jasminum officinale) oil, jojoba(buxus chinensis) oil, kelp, kukui (aleurites moluccana) nut oil,lactamide MEA, laneth-16, laneth-10 acetate, lanolin, lanolin acid,lanolin alcohol, lanolin oil, lanolin wax, lavender (lavandulaangustifolia) oil, lecithin, lemon (citrus medica limonum) oil, linoleicacid, linolenic acid, macadamia ternifolia nut oil, magnesium stearate,magnesium sulfate, maltitol, matricaria (chamomilla recutita) oil,methyl glucose sesquistearate, methylsilanol PCA, microcrystalline wax,mineral oil, mink oil, mortierella oil, myristyl lactate, myristylmyristate, myristyl propionate, neopentyl glycol dicaprylate/dicaprate,octyldodecanol, octyldodecyl myristate, octyldodecyl stearoyl stearate,octyl hydroxystearate, octyl palmitate, octyl salicylate, octylstearate, oleic acid, olive (olea europaea) oil, orange (citrusaurantium dulcis) oil, palm (elaeis guineensis) oil, palmitic acid,pantethine, panthenol, panthenyl ethyl ether, paraffin, PCA, peach(prunus persica) kernel oil, peanut (arachis hypogaea) oil, PEG-8 C12-18ester, PEG-15 cocamine, PEG-150 distearate, PEG-60 glyceryl isostearate,PEG-5 glyceryl stearate, PEG-30 glyceryl stearate, PEG-7 hydrogenatedcastor oil, PEG-40 hydrogenated castor oil, PEG-60 hydrogenated castoroil, PEG-20 methyl glucose sesquistearate, PEG40 sorbitan peroleate,PEG-5 soy sterol, PEG-10 soy sterol, PEG-2 stearate, PEG-8 stearate,PEG-20 stearate, PEG-32 stearate, PEG40 stearate, PEG-50 stearate,PEG-100 stearate, PEG-150 stearate, pentadecalactone, peppermint (menthapiperita) oil, petrolatum, phospholipids, polyamino sugar condensate,polyglyceryl-3 diisostearate, polyquaternium-24, polysorbate 20,polysorbate 40, polysorbate 60, polysorbate 80, polysorbate 85,potassium myristate, potassium palmitate, potassium sorbate, potassiumstearate, propylene glycol, propylene glycol dicaprylate/dicaprate,propylene glycol dioctanoate, propylene glycol dipelargonate, propyleneglycol laurate, propylene glycol stearate, propylene glycol stearate SE,PVP, pyridoxine dipalmitate, quaternium-15, quaternium-18 hectorite,quaternium-22, retinol, retinyl palmitate, rice (oryza sativa) bran oil,RNA, rosemary (rosmarinus officinalis) oil, rose oil, safflower(carthamus tinctorius) oil, sage (salvia officinalis) oil, salicylicacid, sandalwood (santalum album) oil, serine, serum protein, sesame(sesamum indicum) oil, shea butter (butyrospermum parkii), silk powder,sodium chondroitin sulfate, sodium DNA, sodium hyaluronate, sodiumlactate, sodium palmitate, sodium PCA, sodium polyglutamate, sodiumstearate, soluble collagen, sorbic acid, sorbitan laurate, sorbitanoleate, sorbitan palmitate, sorbitan sesquioleate, sorbitan stearate,sorbitol, soybean (glycine soja) oil, sphingolipids, squalane, squalene,stearamide MEA-stearate, stearic acid, stearoxy dimethicone,stearoxytrimethylsilane, stearyl alcohol, stearyl glycyrrhetinate,stearyl heptanoate, stearyl stearate, sunflower (helianthus annuus) seedoil, sweet almond (prunus amygdalus dulcis) oil, synthetic beeswax,tocopherol, tocopheryl acetate, tocopheryl linoleate, tribehenin,tridecyl neopentanoate, tridecyl stearate, triethanolamine, tristearin,urea, vegetable oil, water, waxes, wheat (triticum vulgare) germ oil,and ylang ylang (cananga odorata) oil.

E. Antioxidants

Certain topical formulations of the present invention may also containone or more antioxidants. Non-limiting examples of antioxidants that canbe used with the compositions of the present invention include acetylcysteine, ascorbic acid, ascorbic acid polypeptide, ascorbyldipalmitate, ascorbyl methylsilanol pectinate, ascorbyl palmitate,ascorbyl stearate, BHA, BHT, t-butyl hydroquinone, cysteine, cysteineHCl, diamylhydroquinone, di-t-butylhydroquinone, dicetylthiodipropionate, dioleyl tocopheryl methylsilanol, disodium ascorbylsulfate, distearyl thiodipropionate, ditridecyl thiodipropionate,dodecyl gallate, erythorbic acid, esters of ascorbic acid, ethylferulate, ferulic acid, gallic acid esters, hydroquinone, isooctylthioglycolate, kojic acid, magnesium ascorbate, magnesium ascorbylphosphate, methylsilanol ascorbate, natural botanical anti-oxidants suchas green tea or grape seed extracts, nordihydroguaiaretic acid, octylgallate, phenylthioglycolic acid, potassium ascorbyl tocopherylphosphate, potassium sulfite, propyl gallate, quinones, rosmarinic acid,sodium ascorbate, sodium bisulfite, sodium erythorbate, sodiummetabisulfite, sodium sulfite, superoxide dismutase, sodiumthioglycolate, sorbityl furfural, thiodiglycol, thiodiglycolamide,thiodiglycolic acid, thioglycolic acid, thiolactic acid, thiosalicylicacid, tocophereth-5, tocophereth-10, tocophereth-12, tocophereth-18,tocophereth-50, tocopherol, tocophersolan, tocopheryl acetate,tocopheryl linoleate, tocopheryl nicotinate, tocopheryl succinate, andtris(nonylphenyl)phosphite.

F. Pathological Conditions to be Treated or Prevented

As noted in other parts of this specification, there is substantialevidence that capsaicin would be beneficial in the treatment of a widevariety of pathological conditions. The term “treat” or “treatment”means that the symptoms associated with one or more conditions mentionedabove are alleviated or reduced in severity or frequency and the term“prevent” means that subsequent occurrences of such symptoms are avoidedor that the frequency between such occurrences is prolonged.

Conditions amenable to treatment or prevention with capsaicin arespecifically detailed for post-herpetic neuralgia (Bernstein et al.,1989; Watson et al., 1993), diabetic neuropathy (Capsaicin Study Group,1992), postmastectomy pain syndrome (Watson and Evans, 1992; Dini etal., 1993), oral neuropathic pain, trigeminal neuralgia, andtemperomandibular joint disorders (Epstein and Marcoe, 1994; Hersh etal., 1994), cluster headache (following intranasal application; Marks etal., 1993), osteoarthritis (McCarthy and McCarthy, 1992), anddermatological and cutaneous conditions (Hautkappe et al., 1998).

Examples of pathological conditions responsive to capsaicin therapyinclude, but are not limited to, post-herpetic neuralgia, shingles(herpes zoster), diabetic neuropathy, postmastectomy pain syndrome, oralneuropathic pain, trigeminal neuralgia, temperomandibular jointdisorders, pruritus, cluster headache, osteoarthritis, arthritis pain,rhinopathy, oral mucositis, cutaneous allergy, detrusor hyperreflexia,loin pain/hematuria syndrome, neck pain, amputation stump pain, reflexsympathetic dystrophy and pain due to skin tumor.

Examples of pathological conditions responsive to esters of myristoleicacid include, but are not limited to, arthritis pain, osteoarthritis andinflammation.

It is expected that the novel pharmaceutical composition containingester derivatives of capsaicin and ester derivatives of myristoleic acidset forth herein would be beneficial in the treatment and prevention ofany of the diseases set forth above. One of ordinary skill in the artwould be familiar with the many diseases and conditions that would beamenable to treatment with one or more of the ester derivatives ofcapsaicin set forth herein.

G. Secondary Therapies

Some embodiments of the claimed methods of the present invention involveadministering to the subject a secondary form of therapy in addition toone or more of the therapeutic combination of ester derivatives ofcapsaicin and ester derivatives of myristoleic acid set forth herein.For example, if the disease is a hyperproliferative disease, such ascancer, the secondary therapy may be a chemotherapeutic agent, radiationtherapy, surgical therapy, immunotherapy, gene therapy, or other form ofanticancer therapy well-known to those of ordinary skill in the art. Ifthe disease is an inflammatory disease such as arthritis, exemplarysecondary forms of therapy include non-steroidal anti-inflammatoryagents, steroids and immunosuppressant therapy.

In order to increase the effectiveness of the therapeutic agentdisclosed herein, it may be desirable to combine the therapeutic agentof the present invention with the secondary therapeutic agent. Thesecompositions would be provided in a combined amount effective to providefor a therapeutic response in a subject. One of ordinary skill in theart would be able to determine whether the subject demonstrated atherapeutic response. This process may involve administering thetherapeutic agent of the present invention and the secondary therapeuticagent to the subject at the same time. This may be achieved byadministering a single composition or pharmacological formulation thatincludes both agents, or by administering two distinct compositions orformulations, at the same time, wherein one composition includes theester derivative of capsaicin and ester derivative of myristoleic acidof the present invention and the other includes the secondary agent.

Alternatively, the therapeutic agent of the present invention mayprecede or follow the treatment with the secondary agent by intervalsranging from minutes to weeks. In embodiments where the secondary agentand the ester derivatives of the present invention are separatelyadministered, one would generally ensure that a significant period oftime did not expire between the time of each delivery, such that thesecondary agent and the therapeutic agent of the present invention wouldstill be able to exert a beneficial effect on the subject. In suchinstances, it is contemplated that one may administer both modalitieswithin about 24-48 h of each other and, more preferably, within about12-24 h of each other, and even more preferably within about 30 minute-6h of each other. In some situations, it may be desirable to extend thetime period for treatment significantly, however, where several d (2, 3,4, 5, 6 or 7) to several wk (1, 2, 3, 4, 5, 6, 7 or 8) lapse between therespective administrations.

Various combinations may be employed, the therapeutic agent of thepresent invention is “A” and the secondary agent, such as chemotherapy,is “B”:

A/B/A B/A/B B/B/A A/A/B A/B/B B/A/A A/B/B/B B/A/B/B B/B/B/A B/B/A/BA/A/B/B A/B/A/B A/B/B/A B/B/A/A B/A/B/A B/A/A/B A/A/A/B B/A/A/A A/B/A/AA/A/B/A

Administration of the compositions of the present invention to a patientwill follow general protocols for the administration of therapeuticagents, such as chemotherapy where the disease to be treated is cancer.It is expected that the treatment cycles would be repeated as necessary.

H. Examples

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples which follow representtechniques discovered by the inventor to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

Example 1 Preparation of Butyryl Ester of Capsaicin USP27 (Formula I,R=C₃H₇)

A mixture of 30.5 gm (˜0.1M) of capsaicin USP27 (HUBEI XIANGXI CHEMICALINDUSTRY CO., LTD, China), 16.7 ml (0.12M) of anhydrous triethylamine(Spectrum Chemicals) and 200 ml of anhydrous dichloromethane was placedinto a 1000 ml 2-neck round bottomed flask. The content was covered withaluminum foil to protect it from light exposure. The flask was fittedwith a condenser fitted with a moisture trap on the top and a dropwiseaddition funnel. The flask was kept at room temperature and 12.8 ml(0.12M) of butyryl chloride was added from the funnel into the mixtureslowly with stirring. After the addition, the mixture was refluxed for3-6 hours and stirred for 10-15 hours at room temperature. The mixturewas transferred into a separating funnel and washed successively with2×500 ml of water, 2×500 ml of dilute hydrochloric acid, 2×500 ml of 10%sodium bicarbonate solution and 3×500 ml of type I water. The organiclayer was separated, dried with anhydrous magnesium sulfate and thedichloromethane was removed under vacuum to produce a clear, yellowviscous oil (95% of theoretical).

Example 2 Preparation of Hexanoyl Ester of Capsaicin USP27 (Formula I,R=CH₃—(CH₂)₄)

The compound was prepared essentially as described in Example 1, usingn-hexanoyl chloride instead of butyryl chloride. The product wasrecovered as a low melting viscous yellow oil.

Example 3 Preparation of Palmitoyl Ester of Capsaicin USP27 (Formula I,R=CH₃—(CH₂)₁₄)

The compound was prepared essentially as described in Example 1, usingn-palmitoyl chloride instead of butyryl chloride. The product wasrecovered as a waxy yellow solid.

Example 4 Preparation of a Topical Gel Containing Butyryl Ester ofCapsaicin USP27 and Cetyl Myristoleate

Three compositions of capsaicin butyrate, shown in Table 1, each with abatch size of 500 gm of the gel, were prepared according to thefollowing procedure.

TABLE 1 The Composition of Topical Gel containing Capsaicin ButyrateCOMPOSITIONS INGREDIENTS NAME Amount I Amount II Amount III In asuitable container, the following ingredients were added and mixed witha mixer to make a smooth paste. Purified water 300 ml same samePotassium Sorbate 0.5 gm (0.1%) same same Methyl Paraben 0.5 gm (0.1%)same same Sodium Sodium Citrate 1.5 gm (0.3%) same same Disodium Edetate2.5 gm (0.5%) same same Propyl Paraben 0.05 gm (0.01%) same same SodiumCarbopol Ultrez 10 15.0 gm (3.0%) same same Xanthum gum 1.5 gm (0.3%)same same The following ingredients were mixed together in a separatecontainer and the mixture was added to the above paste with vigorousstirring. Capsaicin butyrate 1.25 gm (0.25%) 2.50 gm (0.5%) 5.0 gm(1.0%) Cetyl Myristoleate 50.0 gm (10%) same same (40%) Tween 80 1.50 gm(0.3%) same same Hallbrite BHB 15.0 gm (3.0%) same same Eugenyl Acetate5.00 gm (1.0%) same same Cyclomethicone 10.0 gm (2.0%) same sameAscorbyl Palmitate 1.50 gm (0.3%) same same Lavender oil 2 ml (0.4%)same same The mixture was stirred thoroughly with a stirrer and thefollowing ingredients were added under stirring. Triethanolamine 8.0 gm(1.6%) same same Purified water qs 500 gm 500 gm 500 gm to make A shinywhite gel was formed and the pH of the gel was between 6.4 and 6.6.

Example 5 Preparation of a Topical Gel Containing Palmitoyl Ester ofCapsaicin USP27 and Cetyl Myristoleate

Three compositions of capsaicin palmitate, shown in Table 2, each with abatch size of 500 gm of the gel, were prepared according to thefollowing procedure.

TABLE 2 The Composition of Topical Gel containing Capsaicin Palmitateand Cetyl Myristoleate COMPOSITIONS INGREDIENTS NAME Amount I Amount IIAmount III In a suitable container, the following ingredients were addedand mixed with a mixer to make a smooth paste. Purified water 300 mlsame same Potassium Sorbate 0.5 gm (0.1%) same same Methyl Paraben 0.5gm (0.1%) same same Sodium Sodium Citrate 1.5 gm (0.3%) same sameDisodium Edetate 2.5 gm (0.5%) same same Propyl Paraben 0.05 gm (0.01%)same same Sodium Carbopol Ultrez 10 15.0 gm (3.0%) same same Xanthum gum1.5 gm (0.3%) same same The following ingredients were mixed together ina separate container and the mixture was added to the above paste withvigorous stirring. Capsaicin Palmitate 2.50 gm (0.5%) 5.00 gm (1.0%)7.50 gm (1.5%) Cetyl Myristoleate 50.0 gm (10.0%) same same (40%) Tween80 1.50 gm (0.3%) same same Hallbrite BHB 15.0 gm (3.0%) same sameEugenyl Acetate 5.00 gm (1.0%) same same Ascorbyl Palmitate 1.50 gm(0.3%) same same Cyclomethicone 10.0 gm (2.0%) Lavender oil 2.0 ml(0.4%) same same The mixture was stirred thoroughly with a stirrer andthe following ingredients were added under stirring. Triethanolamine 8.0gm (1.6%) same same Purified water qs 500 gm 500 gm 500 gm to make Ashiny white gel was formed and the pH of the gel was between 6.4 and6.6.

Example 6 Preparation of Capsules Containing Palmitoyl Capsaicin USP27and Cetyl Myristoleate

The capsule composition is compounded from the following ingredientsgiven in Table 3.

TABLE 3 The composition for the preparation of capsules. IngredientAmount I Amount II Palmitoyl-Capsaicin USP27 5.40 parts 10.8 partsMicrocrystalline Cellulose 19.60 parts 14.20 parts Cetyl MyristoleatePowder 350.00 parts 350.00 parts (20% in corn starch) Ascorbyl palmitate20.00 parts 20.00 parts Silicon dioxide 2.50 parts 2.50 parts Sodiumlauryl sulfate 2.50 parts 2.50 parts Total 400.00 parts 400.00 parts

PREPARATION I: The palmitoyl-capsaicin USP27 (Table 3; Amount I) isintensively milled with ten times its weight of Cetyl Myristoleatepowder, the milled mixture is admixed with the remaining amount of theCetyl Myristoleate powder, microcrystalline cellulose, ascorbylpalmitate sodium lauryl sulfate and silicon dioxide. The mixed powder isagain milled and the composition is filled into 500 mg capsule in aconventional capsule loading machine. Each capsule contains 5.40 mg ofpalmitoyl-capsaicin USP27 (approximately 50,000 SHU equivalent in eachcapsule) and 70 mg of Cetyl Myristoleate and is an oral dosage unitcomposition with effective therapeutic action.

PREPARATION II: The palmitoyl-capsaicin-USP27 (Table 3; amount II) isintensively milled with five times its weight of Cetyl Myristoleatepowder, the milled mixture is admixed with the remaining amount of theCetyl Myristoleate powder, microcrystalline cellulose, ascorbylpalmitate, sodium lauryl sulfate and silicon dioxide. The mixed powderis again milled and the composition is filled into 500 mg capsule in aconventional capsule loading machine. Each capsule contains 10.8 mg ofpalmitoyl-capsaicin USP27 (approximately 100,000 SHU equivalent in eachcapsule) and 70 mg of Cetyl Myristoleate and is an oral dosage unitcomposition with effective therapeutic action.

Example 7 Toxicity Assessment of the Inventive Composition

A 0.5% of butyryl-capsaicin USP27 and 4% Cetyl Myristoleate gel asdescribed in example 4 was applied to the forearm of 10 healthyindividuals twice daily for a two-week period in an outpatient clinic.No patients complained of burning, irritation, scaling or redness afterthe cream. Patients returned to the clinic after having used the gel fortwo weeks for a visual inspection of the forearm area. The examiningphysician noted no redness, irritation or scaling in the area where thesolution had been applied.

Example 8 Treatment of Pain with the Topical Formulation of Butyrylcapsaicin USP27 and Cetyl Myristoleate

Case I. Patient with Diabetic Neuropathy in the Feet

A 53 year old hispanic male has developed Type 2 diabetes a year ago andhas diabetic neuropathy in the feet. He was given the 0.5%butyryl-capsaicin USP27 and 4% Cetyl Myristoleate gel and the followingis his testimony on the effectiveness of the oil for the treatment ofcold sores. “I was diagnosed with type 2 diabetes last year. I also haveneuropathy in my feet. I had an ulcer on my foot and was treated by alocal pediatric doctor in San Antonio. My ulcer has since been clearedup. I control my diabetic ailment with a low-carb diet only, with nomedication. I have also lost 40 lbs. since my diagnosis last year. Ihowever feel pain on the bottom of my feet at times. Since taking thecream by application on my feet, I have noticed much less discomfortthan usual. The comfort that I noticed has lasted up to 24 hrsper-application. This cream really helps my condition and would like tolet your research company to know about your product”.

Case II. Patient with Pain in Dislocated Finger

A 45 year old white male developed constant pain in the finger due todislocation and has to be injected cortisone every 3 months to alleviatethe pain. He was given 1% butyryl capsaicin USP27 and 4% CetylMyristoleate gel for topical application. He gave the followingtestimony about the treatment. “Every 3 months or so, I have a cortisoneshot in a finger I dislocated a few years ago. I used the 1% gel givento me. It did a very good job for the pain and making movement a loteasier. The swelling was reduced as well as the pain. I did however,find that the product does have a tendency to get a little warm. That'sa good thing, other than it still transfers after hand washing, and youmight get a little warm where you don't need it. I feel like thisproduct would be beneficial for people who can not or who would rathernot take oral pain medication”

Case III. Patient with Severe Diabetic Neuropathy

A 40 year old white female developed diabetic neuropathy in 2000 and wasgiven 0.5% butyryl capsaicin and 4% Cetyl Myristoleate gel for treatingher pain in the feet. She gave the following testimony about thetreatment. “I was diagnosed with neuropathy in 2000. There never hasbeen much they could do for me other than give me pain medication that'saddictive. At this time, I'm on Neurontin 1800 mg a day, Vicodin 5-6tablets a day. Diclofenac 150 mg a day, and also get injections in myfeet. In the last 7 months I have had 5 different cast on my left foot.Since my left foot has a cast my right foot has become worse because allof my weight has been on my right foot. I used the crème and within 30min. I could feel the difference. Later I was up walking and realizedthere was no pain at all. At night I don't sleep well because of thepain, but I was able to go to sleep the whole night through withoutcramps and pain. My cast will be coming off in 8 days and I can't waitto try it on my left foot”.

Case IV. Patient with Pinched Nerve Pain

A 65 year old white female developed pain due to pinched nerve and wastreated with the 0.5% butyryl capsaicin USP27 and 4% Cetyl Myristoleategel. She gave the following testimony about the treatment. “Over aperiod of years, periodically a pinched nerve would occur in the leftlower side of my back. This required chiropractic treatment which attimes was not always successful requiring several additional treatments.After using the cream, my pain has disappeared and that was three daysago and still no pain”.

Case V. Patient with Severe Diabetic Neuropathy

A 49 year old white male developed diabetic neuropathy in 2001 and wasgiven 0.5% butyryl capsaicin USP27 and 4% Cetyl Myristoleate gel fortreating his pain in the feet. He gave the following testimony about thetreatment. “I have diabetic neuropathy brought on by extreme intravenousapplication of antibiotics for a six day period. Since that time I haveexperienced unmanageable pain causing sleep depravation, anxiety with norelief on the market. Prescriptions for anti-depressants were given bymy personal physician but to no avail. Now with this cream I can sleepwithout any disturbances. Nothing on the market today could help mewithout the use of addicting narcotics that were marginally effective atbest”.

Case VI. Patient with Severe Neuropathy

A 62 year old white female developed neuropathy in 1975 and was given0.5% butyryl capsaicin USP27 and 4% Cetyl Myristoleate gel for treatingher pain in the feet. She gave the following testimony about thetreatment. “My neuropathy numbness in feet and hands first started afterback surgery in 1975 my L 4 and 5 were fused and some disks removed. Thenumbness and pain increased after surgery for a double mastectomy whichwas botched by a Doctor inexperienced at this surgery in 1988 causingsever pain in my abdominal muscles and up my chest. In 1992 I was in thehospital for depression a new Doctor prescribed Percocet medication formy pain. The Percocet helped but I had to take 8 a day 5/325 mgs withanti depression medication at the time. The pain was so overwhelmingafter 4 years that I decided one day to end it all and I was found by myhusband on the floor. I had kept my pain a secret over the 4 yearshoping it would just eventually go away and I had never told my familythat I was suffering so much. I had overdosed with the Percocet in anattempt to end my pain for good. I recovered some and I tried to cutback on the Percocet and got down to 1 a day to prevent addiction. Theincrease in pain and numbness was causing me to stumble when I walked. Aneurologist in 1998 suggested that I try Neurontin which is used forepilepsy. I think I was taking 100 mgs 3 times a day at first thenincreased in 6 weeks to 200 mgs 3 times a day, when that failed we wentup to 300 mgs 3 times a day. The 300 mgs was starting to help some butthey had to increase to 800 mgs 5 times a day to really help my pain.This helped more than the Percocet alone but I still needed to keep thePercocet at reduced amounts. I fell and broke my back fusion in 2000.New back surgery attempted to fuse my back again but in 2003 doctors hadto use rods and pins to secure it. With each surgery my numbness andpain would increase. I tried water therapy and various physicaltherapies but nothing could relieve my pain. I have had other injuriesas well, in 2002 a broken right ankle and compression fracture in myright knee and in 2003 I broke my left ankle. In October 2005 a Doctorspecializing in neurological disorders said the Neurontin was probablyweakening my bones and switched me to a generic version of the samemedication and dropped the dose to 50 mgs a day. My pain increasedimmediately and I went through withdrawals with the smaller dose. ThisDoctor said if the pain didn't decrease I was to increase one tabletmore a day each week till the end of the 4^(th) week and return to him.I never went back to this Doctor and just increased back to 800 mgs 5times a day to coupe with the pain, burning, and itching feelings. I hadto take depression medication again at this time. I tried a new topicalcream just this week Jul. 11, 2006 being developed in San Antonio, Tex.One of my most disruptive symptoms in my feet would cause me toinvoluntarily jump in bed and I was beginning to feel this come on whenI applied the cream to my left foot. The symptoms just stopped! Usuallythis symptom would last several hours to even days. I have burningsensations in both hands and up my forearm but after applying this creamI had my first relief from that burning feeling since my back surgeriesin 2003! This cream has done more to relieve my symptoms than bothPercocet and Neurontin has ever done for me! I now have renewed hope tostop taking all this internal medication that is bound to hurt my liverand is weakening my bones”.

1. A pharmaceutical composition comprising: (a) a compound of formula (Ia):

wherein R₁ is selected from the group consisting of (CH₂)₄(CH)₂CH(CH₃)₂ (capsaicin ester); (CH₂)₅(CH)₂CH(CH₃)₂ (homocapsaicin ester; (CH₂)₅CH(CH₃)₂ (nordihydrocapsaicin ester); (CH₂)₆CH(CH₃)₂ (dihydrocapsaicin ester); (CH₂)₇CH(CH₃)₂ (homodihydrocapsaicin ester); (CH₂)₆CH₃ (n-vanillyloctanamide ester); (CH₂)₈CH₃ (n-vanillyldecanamide ester); and (CH₂)₄(CH)₂CH(CH₃)₂ (civamide ester) and (b) an ester of myristoleic acid of formula (Ib):

wherein R of formula (Ia) and (Ib) are independently is selected from alkyl groups of up to about 18 carbon atoms and aryl groups of up to about 18 carbon atoms and alkylene group of up to about 18 carbon atoms and an arylene group of up to about 18 carbon atoms, with the proviso that when R of formula (Ia) is alkyl, it is not methyl, wherein the alkyl, aryl and alkylene groups may be substituted or unsubstituted, branched or straight chains, wherein R may contain heteroatoms such as O, N, Cl, F, Br, I and S and may be straight chained or branched.
 2. The pharmaceutical composition of claim 1 wherein R of formula (Ia) and (Ib) are independently selected from the group consisting of ethyl, propyl, butyl, hexyl, heptyl, octyl, dodecyl, 1-pentadecyl, 1-heptadecyl, 1-hexadecyl, 1-octadecyl, isopropyl, sec-butyl, t-butyl, 2-methylbutyl, 2-pentyl, 3-pentyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, vinyl (ethenyl), 1-propenyl, i-butenyl, pentenyl, hexenyl, n-decenyl, —CH₂—CH₂—COOH and c-pentenyl groups.
 3. The pharmaceutical composition of claim 1, wherein the ratio of an ester of capsaicin to an ester of myristoleic acid is from about 99:1 to 1:99.
 4. The pharmaceutical composition of claim 1, wherein the composition comprises one or more or more pharmaceutically acceptable antioxidants.
 5. The pharmaceutical composition of claim 4, wherein the antioxidant is selected from the group consisting of ascorbic acid, sodium ascorbate, sodium bisulfite, sodium metabisulfate, curcumin, curcumin derivatives, ursolic acid, resveratrol, resveratrol derivatives, alpha-lipoic acid and monothioglycerol.
 6. The pharmaceutical composition of claim 4, wherein the composition comprises one or more pharmaceutically acceptable preservatives and/or buffering agents.
 7. The pharmaceutical composition of claim 6, wherein the buffering agent is selected from the group consisting of monobasic and dibasic sodium phosphate, sodium benzoate, potassium benzoate, sodium citrate, sodium acetate and sodium tartrate.
 8. The pharmaceutical composition of claim 6, wherein the preservative is selected from the group consisting of methylparaben, methylparaben sodium, propylparaben, propylparaben sodium, benzalkonium chloride and benzthonium chloride.
 9. The pharmaceutical composition of claim 8, wherein the pharmaceutical composition comprises one or more pharmaceutically acceptable polysaccharides.
 10. The pharmaceutical composition of claim 9, wherein the polysaccharide is selected from the group consisting of dextran sulfate, pectin, modified pectin, insoluble 1,3-β-D glucan, micronized 1,3-β-D glucan, soluble 1,3-β-D glucan, phosphorylated 1,3-β-D glucan, aminated 1,3-β-D glucan and carboxymethylated 1,3-β-D glucan, sulfated 1,3-β-D glucan, insoluble 1,3/1,6-β-D glucan, micronized 1,3/1,6-β-D glucan, soluble 1,3/1,6-β-D glucan, phosphorylated 1,3/1,6-β-D glucan, aminated 1,3/1,6-β-D glucan and carboxymethylated 1,3/1,6-β-D glucan and sulfated 1,3/1,6-β-D glucan.
 11. The pharmaceutical composition of claim 1, wherein the pharmaceutical composition comprises an amount of compound of part (a) selected from the group consisting of from 0.025% to 20% by weight, from 0.05% to 20% by weight, and from 0.05% to 10% by weight.
 12. The pharmaceutical composition of claim 1, wherein the compound of part (a) is capsaicin palmitate.
 13. The pharmaceutical composition of claim 12, wherein the myristoleic acid ester of part (b) is cetyl myristoleate.
 14. The pharmaceutical composition of claim 13, wherein the composition is formulated for topical administration.
 15. The pharmaceutical composition of claim 14, wherein the composition comprises a pharmaceutically acceptable excipient selected from the group consisting of butyloctyl salicylate, polyacrylic acid, eugenyl acetate, eugenyl acetate, polyoxyethylene sorbitan monooleate, xanthum gum, lavender oil, triethanolamine, disodium edentate, methyl paraben sodium, propyl paraben sodium, potassium sorbate and combinations thereof.
 16. The pharmaceutical composition of claim 1, wherein the Compound of part (a) is selected from the group consisting of capsaicin ester, homocapsaicin ester, nordihydrocapsaicin ester, dihydrocapsaicin ester and homodihydrocapsaicin ester and wherein R is selected from the group consisting of an alkyl group of up to 18 carbon atoms, an aryl group of up to 18 carbon atoms, an alkylene group of up to 18 carbon atoms and an arylene group of up to 18 carbon atoms, wherein the alkyl, aryl and alkylene groups may be substituted or unsubstituted, branched or straight chains, wherein R may contain one or more heteroatoms such as O, N, Cl, F, Br, I and S and may be straight chained or branched. 